<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
        #a{width: 1000px;height: 200px;background: #345;border:1px solid #555}
        #b{width: 800px;height: 100px;margin: 100px;background: #543}
        #c{width: 1000px;height: 200px;background: #453;border: 1px solid #555}
        #d{width: 800px;height: 300px;background: #645}
    </style>
</head>
<body>
    <div id="a">
        <div id="b"></div>
    </div>
    <div id="c">
        <div id="d"></div>
    </div>
</body>
</html>